His conclusion: The movie posters for the highest-grossing NC-17, R, PG-13 and PG movies (with one exception -- Shrek) are all dominated by the color black, a color that is generally "feared" by design clients as being too dark and gloomy.

Flesh tones came in second. (Flesh is not so feared because baby, sex sells.)

What's missing from this analysis, of course, is the distribution of black across all the other movie posters. Without knowing that, it's dicey to conclude that correlation implies causation.